1. Field of the Invention
The present invention relates generally to material handling apparatus, and more particularly to apparatus for rapidly, accurately and repetitively dispensing batches of articles of predetermined weight or quantity.
2. Prior Art
Articles are frequently packaged in batches of predetermined weight or quantity. Due to the number and diversity of small articles which are packaged in batches, apparatus capable of rapidly, accurately, and automatically dispensing successive batches of articles is in demand.
Previously proposed apparatus for dispensing batches of articles have suffered one or more of the drawbacks of inadequate operating speed, weighing inaccuracy and/or inconsistency, vibration sensitivity, and lack of versatility in handling differing types of articles and article weights.
While proposals have been made to use vibratory feeding systems to deliver articles to a weighing or counting apparatus, problems have been encountered in successfully implementing such proposals. One problem has been that of stopping the feed of articles into the weighing or counting apparatus immediately after a predetermined weight or count of articles has accumulated. Often some articles have already begun discharging from the vibratory feeding equipment into the weigher or counter at the time a desired weight or count of articles has accumulated. In some systems, efforts are made to divert such tardily discharging articles into an overfeed receptacle from which they are returned to the vibratory feeder. There are instances when the tardily discharging articles enter the weigher or counter and cause the accumulated batch to have an excessively large weight or count.
Proposals to overcome this problem of weighing or counting inaccuracy attempted to feed articles into an accumulator bucket at an initially high feed rate to bring the weight or quantity of articles rapidly toward a desired amount. When the weight or quantity was close to the desired amount, the feed rate was reduced until the targeted amount was achieved. Such proposals have achieved some improvements in article handling speed and accuracy. An apparatus of this type is described in the referenced Dispenser Patent. These proposed systems have often required two or more independently operating feeder systems.
A problem encountered where vibratory feeding equipment is used with weighing and certain counting apparatus has been that the operation of the apparatus may be adversely effected by vibrations generated in the feeding equipment. A counting apparatus which is not subject to vibration-induced error and which can be used in the environment of vibratory systems is described in the referenced Counting Head Patent. With weighing systems, however, separate, relatively massive vibration isolating mounting systems have been used to support the feeder and the weighing equipment in an effort to reduce vibration-caused weighing errors.
Where vibrations are transmitted from vibratory feeding equipment to a weighing apparatus, the time required to weight a quantity of articles has often had to be extended to assure accuracy. In some weighing systems, article weight is determined by integrating sensed weight over an interval of time as long as several seconds to improve accuracy. The extended weighing time requied by such systems necessitates correspondingly slow feeder rates and the speed of operation of such systems is undesirably slow.
Achieving acceptable operating speeds together with weighing or counting accuracy is rendered more difficult where the apparatus must be capable of handling a wide range of article sizes, together with a wide range of article accumulation weights or counts. While some prior systems are reasonably effective in handling articles of a given size and weight for dispensing within a given range of article accumulation weights or counts, these systems are often not well adapted to handle articles of significantly different sizes and weights and/or significantly smaller or larger article accumulation weights or counts.
Another problem with prior apparatuses is that the accumulator buckets employed in their weighing or counting systems typically overlie or nearly overlie other supporting or operating components of the apparatus. Stated in other terms, the accumulator buckets of self-supporting apparatuses which do not have to be anchored to a supporting surface have an inadequate overhang in relation to nearby apparatus components to permit a direct discharge from such buckets into conveyors, packaging equipment and the like. Special chutes must accordingly be constructed to interface proposed apparatuses with such receptacles and other equipment.